I had jira custom fields are working differently

[Aditya Satpurkar]

I had 2 customfields which can have multi select values, but now it is coming up as a list with all the values with a checkmark on left 
It used to be like a single field where you can search and add multiple values
Now the box is replaced by a list of values
we have a lot of values of fields so cannot work with this list type
Type of customfield is checkbox

[Aditya Satpurkar]

Did not get any solution yet